Plant cell wall is required not only for the structure to determine the actual shape of cells and functional properties to control inner and outer cellular communication but also for overall growth and tree expansion. Cellulose is the most significant component of plant cell walls.
Starch is an energy storage polysaccharide found in plants.Plants need energy to grow.They use energy from sunlight to make a simple sugar, glucose.Plants make polymers - starch - out of extra glucose,so it's right there when they need it.